1. Field of the Invention
This invention relates in general to drilling and production of oil and gas wells, and in particular to a design of a cost effective rapid makeup connector for tubular members using a threaded collapsible collet or ring.
2. Brief Description of Related Art
A drilling riser is a large diameter pipe used in offshore drilling operations to guide the drill string from the offshore platform to and from the subsea wellhead and to provide means for circulation of drilling fluid. The drill string is lowered through the drilling riser. Drilling fluid circulates down from the platform through the drill string, out through the drill bit, and returns to the platform in the space between the inner diameter of the riser and the outer diameter of the drill string. Environmental forces caused by waves, currents, and the movement of the offshore platform, as well as internal forces caused by the weight of the heavy drilling fluids, all contribute to the substantial loads applied to the drilling riser. Additionally, high pressure drilling risers, utilizing surface blowout preventers, may be exposed to full wellbore pressure. The connection between each successive joint of drilling riser must be able to withstand such loads.
The prior art makes up the riser pipe or joint connections with bolted flange type connectors or with radially oriented screws that move dogs into and out of engagement with a profile on the riser pipe. Both of these methods require manipulation with a wrench or stud tensioning device, placing personnel in close proximity to the drilling slots for prolonged periods of time, and increasing the danger level of performing the task.
Other prior art methods involve use of screw type box and pin ends that require the rotation of the riser members through multiple turns in order to torque the tubular members into a secure connection. As with the previously discussed methods, these connection types require manipulation with a wrench device, continuing to place personnel in close proximity to the drilling slots for prolonged periods of time, and increasing the danger level of performing the task. Where the riser diameters are larger, the torque requirements for providing typical separation forces for a conventional direct threaded make-up are extremely high. Still further, the time necessary to either bolt riser joints together, screw locking dogs into engagement, or screw box and pin end joints into engagement can be quite long. This can add significantly to the overall time needed to operate the rig, greatly increasing the costs of the project.
In another prior art embodiment the riser box ends are formed with pockets and locking members positioned within the pockets. The locking members have a profile that mates with a profile on a pin end of the adjacent riser. This riser assembly includes a special cam ring that is actuated by specialty equipment on the platform. The specialty equipment causes the cam to move the locking members into engagement with the profile of the pin end to secure the riser tubulars. These cam assemblies may significantly increase the cost of the platform due to the increased capital costs for the special equipment and more expensive riser members. Therefore, a riser joint that allows for a strong connection that can be rapidly made-up without placing personnel in close proximity to the drilling slots for prolonged periods of time and at a lower capitol cost would be desirable.